“What do you call someone who speaks three languages?”

“Trilingual.”

“What do you call someone who speaks two?”

“Bilingual.”

“And what do you call someone who speaks only one?”

“American.”

It’s an old joke — and I once hear it from someone who mocked her own countrymen by changing the punch line to “French.” It’s here because I’ve been wondering about how many Americans are able to speak more than one language.

A 2001 Gallup poll said that about 1 American in 4 can hold a conversation in a second language.  Looking at the topic from a different angle, a 2007 report from the Bureau of the Census said that “of 281.0 million people aged 5 and over, 55.4 million people (20 percent of this population) spoke a language other than English at home.”

Of those 55.4 million, about 31 million claimed to speak English “very well”, and another 11 million said “well.”

It’s something of a moving target, then, depending on how you define bilingual. I focused on it after seeing an article by science writer Catherine de Lange. The version I first saw appeared in the Washington Post, based on a longer piece de Lange wrote in New Scientist (paywall).  De Lange’s mother, who was French, spoke French to her from infancy, and the articles have to do with the effects of bilingualism on the brain.

One study she mentions discussed “a profound difference [in brain imaging] between babies brought up speaking one language and those who spoke two.”  In essence, researcher Laura Ann Petitto says, the babies’ bilingualism seems to “wedge open” the window for learning language, making it easier for them to acquire new languages through life.

And there’s this (from de Lange’s Washington Post article):

Ellen Bialystok, a psychologist at York University in Toronto, first stumbled upon one of these advantages while asking children to spot whether various sentences were grammatically correct. Both monolinguals and bilinguals could see the mistake in phrases such as “apples growed on trees,” but differences arose when they considered nonsensical sentences such as “apples grow on noses.” The monolinguals, flummoxed by the silliness of the phrase, incorrectly reported a grammar error, whereas the bilinguals did not.

One explanation (based on work by Viorica Marian and her colleagues) is that the two languages “are constantly competing for attention in the back of the [bilingual] mind.” As a result, the brain is constantly getting “the kind of cognitive workout…common in many commercial brain-training programs.”  (Those programs require you to ignore distracting information.)

What about the long-term effect of this competition?  De Lange reports that Bialystock and colleagues found that bilinguals were slower than their monolinguals peers to show signs of Alzheimer’s — by four to five years, even after taking in factors like occupation and education.

So possibly all that activation strengthens the brain in a way that helps it resist the disease.  Not that you should try learning another language as a form of medication–though if that’s the way you look at it, enjoy.

More speculative, but just as interesting were de Lange’s comments on how a bilingual person can express himself — can behave, so to speak — differently in the two languages.  There’s a hint that the person may have the mental equivalent of two channels, one for each language.

Which probably bodes well for the bilingual Karen Matheson, who sings Canan nan Gaidheal (The Language of the Gaels).  (The song tells of the Western Isles — the Outer Hebrides — the stronghold of Scottish Gaelic.)

http://www.youtube.com/watch?v=RXWHo7doNQ8